Angioplasty is an established procedure for removing atherosclerotic plaque from the arterial walls within the vascular system of the patient. The plaque is minimized by use of a catheter that is inserted into the site of the diseased-occluded vessel. A balloon portion of the catheter is then inflated to a predetermined pressure range and size, to radially compress the plaque occlusion, thereby increasing the internal diameter of the previously restricted artery. The balloon is then collapsed and the catheter is removed.
After the angioplasty procedure has been performed, about one-third to one-half of the patients soon develop restenosis. Restenosis is the condition which may occur after angioplasty, with or without stenting, wherein the proliferation of cells cause a restenotic lesion to form, resulting in the further blockage of the intravascular structure.
Various systems and techniques have been devised to treat restenosis:
U.S. Pat. No. 5,059,166 (Fischell et al.) discloses a system for delivering a solid radioactive isotope through a helical coil that is integral with a catheter balloon to inhibit intimal hyperplasia. PA1 U.S. Pat. No. 5,213,561 (Weinstein et al.) discloses a catheter system for preventing restenosis by exposing the lesion to a solid radiation material mounted on the distal end of a guide wire disposed upon a catheter. PA1 U.S. Pat. No. 5,302,168 (Hess) and U.S. Pat. No. 5,411,466 (Hess) disclose a method and an apparatus for restenosis treatment involving a plurality of radioactive elements disposed about the circumference of the catheter, or disposed within the central lumen. PA1 deliver a predetermined totally-cumulative and homogenous dose of radiation to the lesion site, at a predetermined penetration depth, while minimizing the exposure of surrounding healthy tissue to the radiation; PA1 enable the treating physician or other health-care personnel to be bedside to the patient during the administration of the radiation therapy without exposing the physician or health-care personnel to any reasonable risk; PA1 use radiation material that is readily and inexpensively available from a commercial provider; PA1 use minimal special equipment storage, or delivery devices, except for routine facilities available in most nuclear medicine or radiation oncology departments; PA1 use a radiation carrier material that if applied as an unsealed free-gas form, the inert, noble gas properties essentially enable the molecules of the carrier material to rapidly dissipate throughout the body of the patient without any prolonged organ accumulation or chemical interaction, and rapid dilution of the carrier material is quickly rereleased from the bloodstream through the lungs; PA1 not occlude normal blood flow during therapy, thereby providing more flexibility as to administration time and dosage; PA1 use a radiation carrier material that is a stable and which can be pressurized, stored, and made to high millicurie activity per cubic centimeter with reasonable cost and availability; PA1 use beta particles having excellent initial dose rate delivery and energy transfer when directly adjacent to the targeted tissue with the first one millimeter, and not penetrate much beyond this depth; PA1 use gamma photon energies having decay fractions that provide complementary dose deposition with the beta particles for the first one millimeter, and primary additive dose delivery for an additional two to three millimeters of the targeted tissue; and PA1 use beneficial physical and biological radiation properties for treating restenosis, and malignancies (for example--in the brain, lung, esophagus, trachea, cervix, biliary ductal system, colon or rectum, the gastrointestinal system, the gynecological system, or head and neck) and other internal ailments where an internal application of radiation directly applied to the tissue may be needed.
Also, radiation therapy is commonly administered to cancer patients to locally control or destroy malignant tissue. Oftentimes, radiation that is administered to cancer patients externally unavoidably destroys healthy tissue surrounding the tumor.
A system is needed that will: